The string of emissions tampering investigations press on and the latest car company to be scrutineered is General Motors. In a report by Bloomberg, owners of Chevrolet Silverado HD and GMC Sierra HD pickups claim that at least three defeat devices were installed in their vehicles.

Over 705,000 owners and lessees have filed a 190-page complaint, claiming that the emissions their pickups put out are five times more than the legal limit set by the Environmental Protection Agency (EPA). The suit alleges that the diesel-powered pickups have been rigged to pass emissions testing. 2011 to 2016 models were allegedly fitted with the defeat device.

In response, General Motors has released a statement saying, “These claims are baseless and we will vigorously defend ourselves”. The company added that their diesel-powered heavy-duty pickups are in compliance with EPA and California Air Resources Board (CARB) standards.

The engine in question is the 6.6-liter Duramax V8 turbodiesel. In General Motors' website, the said engine has drastically reduced emissions when compared to its predecessor. To run cleanly, it uses a particulate filter, as well as urea injection to clean off the impurities from diesel exhausts.

This week alone, two other manufacturers have had lawsuits filed against them for emissions tampering. Two days ago, 11 offices of Daimler AG were raided by German authorities regarding the alleged fraud. Yesterday, US Department of Justice says defeat devices were found in select diesel Fiat Chrysler Automobiles pickups and SUVs.